Variable area propulsive nozzle means for power plants



VARIABLE AREA PROPULSIVE NOZZLE MEANS FOR POWER PLANTS Original Filedllay 22, 1943 Inven-tor Nathan C. Price ram pressure and Patented Nov.8,1949 I VARIABLE AREA PROPULSIVE NOZZLE MEANS FOR POWER PLANTS NathanC. Price, Los Angeles, Calif., assignor to Lockheed AircraftCorporation, Burbank, Calif.

Original application May 22, 1943, Serial No. 488,029, now Patent No.2,468,461, dated April 26, 1949. Divided and this application March 10,1945, Serial No. 581,994

21 Claims. (01. so-35m This invention relates to prime movers and hasmore particular reference to nozzle constructions for internalcombustion reaction type power plants. This application is a division ofmy copending application, Serial No. 488,029, filed May 22, 1943, nowPatent No. 2,468,461, which is a continuation in part of my copendingapplication, Serial No. 433,599, filed March 6, 1942. The presentinvention is intended primarily for embodlment in power plants ofaircraft and other high-speed vehicles in which propulsion is producedby the reactive effect of a high velocity gas jet.

In my copending applications above identified, I have disclosed a powerplant comprising, briefly, multi-stage air compressors, a combustionchamber receiving the compressed air from the compressors, a gas turbinereceiving the expanding gases of combustion from the chamber and servingto drive the compressors, and a nozzle arrangement for discharging thegases from the turbine in the form'of a reactive propulsive jet. Thespeed of operation of the gas turbine and consequently of thecompressors, is dependent to a substantial extent upon the backpressures imposed on the turbine by the nozzel means, and by varying theeffective area of the nozzle the speed of operation of the gas turbineand compressors may be controlled. During operation of the unit, thetemperature in the secondary combustion chamber and nozzle varies, as aresult of supplemental fuel injection, and the temperature in the nozzleis affected by conditions in the zone of intermediate fuel injection asinfluenced by the ambient air temperature. Such variations in thetemperature at the nozzle are reflected in deviations in turbine andcompressor speeds. For example, an increase in temperature of the gasespassing through the nozzle is accompanied by an increase in volumetricflow which in turn increases the back pressure on the turbine. It is ageneral object of the present invention to provide a power plantof theclass referred to embodying an eflicient nozzle for discharging thecombustion gases in the form of a high velocity reactive propulsive jetwith means for varying both the efiective length and area of -.thenozzle to control the speed of operation of the gas turbine and governthe general operation of the power plant as a whole. The nozzleandthroat means of the invention is operable to control the back pressureon the turbine and to compensate for nozzle temperature changes tomaintain or control turbine and compressor speed.

It is another object'of the inventionto provide a nozzle constructionfor gas reaction power plants characterized by novel means for varyingthe operative length and efl'ective area of the nozzle. The constructionincludes two spaced and interconnected throat members movable withrespect to a constriction in the nozzle to control the cross sectionalarea and the effective length of the nozzle.

It s another obiect of the invention to provide a nozzle of thecharacter referred to having a sensitive remote control system for themovable throat elements embodying a cylinder and piston mechanismassociated with one of the throat members. The manual control includes avalve remotely controlled by the operator or an automatic governor andserving to govern the bleeding of actuating fluid from one side of thepiston, the positionof the throat member being determined by theopposing frictional forces of the nozzle gases acting upon the throatmembers and the unbalanced fluid pressures at opposite sides of thepiston. The point of equilibrium of these opposing forces is determinedby the settin or position of the remotely controlled valve.

A further object of the invention is to provide a nozzle of the classabove referred. to having simple, yet very effective means for coolingone or both of the throat members. The .actuating air under pressuresupplied to the cylinder and piston means of the actuating mechanism isbled, in part, through the throat members to cool the same.

A still further object of the invention is to provide a nozzle means ofthe character described embodying novel internally cooled throat members of reractory material having cooling-air discharge orifices forproviding boundary layers view taken substantially as indicated by line2-2 on Figure 1;

Figure 3 is a cross sectional view of the piston and one of thesupporting rods; and

Figure 4 is a fragmentary sectional view of a portion of the nozzlemeans and adjacent portion of the turbine. v

The nozzle means of the invention is adapted 159 be employed inassociation with the gasturblue of an internal combustion reaction typepower plant and is operable to influence the action of the power plantas a whole. The embodiment of the invention disclosed in the drawing andherein described may be considered as an element of a power plant of thecharacter described in my copending application, Serial No. 488,029, itbeing understood that the invention is capable of considerable variationto adapt it for use on reactive type power plants of diiferent sizes,types, etc.

The nozzle structure includes a secondary combustion chamber S providedimmediately at the rear of the gas turbine of the power plant and whichincludes an elongate cylindrical housing 2 adapted to be secured to thegas turbine housing by a bolt or screw connection 246. The tubularhousing 24! is equipped with a lining 242 composed of carborundum orother suitable refractory 'material. An annular baffle 243 is supportedwithin the chamber S in concentric relation to its lining 242.Circumferentially spaced streamlined struts 245 rigidly support thebaffle 243 in the chamber. The battle is constructed of refractorymaterial or heat resistant metal and is streamlined or airfoil shaped inlongitudinal cross section. The streamlined baffle 243 is in spacedsurrounding relation to the cap 230 of the turbine rotor and istherefore in surrounding relation to the annular series of supplementaryfuel orifices 235. Supplemental fuel is supplied to the hollow shaft I46of the turbine rotor l6! and passes through orifices 231 in the cap 236to discharge from the orifices 235. The secondary combustion chamberequipped with the airfoil shaped baffle 243, utilizes the kinetic energyof the residual velocity of the gas issuing from the gas turbine, torender this energy additive to the kinetic energy of the propulsive jet.It will be observed that the baffle protects the housing 24! in the areaof introduction of the supplementary fuel and being spaced from thelining 242 leaves an annular passage for carrying relatively cool gaseswhich form a boundary layer along the surface of the lining, thusfurther protecting the housing.

The nozzle N includes the above described tubular housing 24l and itslining 242, the housing and lining extending rearwardly a considerabledistance beyond the secondary combustion chamber. The rear portion ofthe housing 2 is shaped to have an internal contraction or throatrestriction 250. The refractory lining 242 continues over the surfa e ofthe throat constriction to protect the same. The nozzle means furtherincludes axially spaced tubular throat members 246 and 241. The member246 is within the housing 24l at the upstream side of the throatconstriction, and is streamlined or airfoil shaped in longitudinal crosssection. The throat member 241 is at or beyond the rear end of theconstriction 250 and presents a, cambered or curved convex innersurface. The minimum diameter of this curved surface is substantiallythe same as the minimum effective diameter of the constriction 250. Asshown in Figure 1, the exterior of the throat member 246 may besubstantially cylindrical, while the inner surface is cambered and hasan efiective diameter shorter than the eilective diameter of the throatrestriction 250. The throat members are formed of or protected byrefractory material or heat resistant metal and are hollow for coolingpurposes as will be later described.

The longitudinally spaced throat members are supported for axialmovement and are connected for movement in unison. A plurality ofcircumferentially spaced longitudinally extending hollow rods 248connect the throat members 246 and 241, and slidably operate inlongitudinal bearing channels 249 in the throat portion 250 of thehousing 2. The outer throat member 241 is also slidably supported andguided on spaced hollow piston rods 25!. The forward ends of the pistonrods 25! are fixed to fittings 252 on the rear end of the nozzle housing24!. The rear portions of the piston rods 25l' extend into a tubularcylinder 254 arranged or formed within the hollow throat member, and therods are fixed to an annular piston 253 within the cylinder. It will beseen that the throat member 241 and its cylinder 254 are reciprocablerelative to the fixed piston 253.

The interconnected throat members 246 and 241 are movable axially tovary the length and efiective area of the nozzle and the inventionprovides a remotely controllable fluid pressure actuated system fordetermining the positions of the members. This system includes alongitudinal passage 255 in at least one of the piston rods 25lextending from the forward end of the rod to lateral ports 211 whichcommunicate with the annular cylinder 254 at the rod side of the piston253. Figure 3 illustrates this construction. A pipe or tube 256 conductsair under substantially constant pressure to the passage 255 fordelivery to the rod end of the cylinder. The tubing 256 is supplied withthe air under pressure from a selected stage of the air compressor, orfrom another suitable pressure source.

The control system for governing or determining the longitudinalposition of the throat members 246 and 241 includes provision forsupplying air under pressure to the rear side of the piston 253 tobalance, or partially balance, the pressure at the forward side of thepiston. In the preferred construction, this means comprises a duct 216of relatively small capacity extending longitudinally through the pistonto connect the forward and rearward ends of the cylinder 254. Thecontrol system further includes a remotely operable valve forcontrolling the bleeding of air from the rear end of the annularcylinder 254. The rear portion of the throat member 241 has an internalcavity 268 vented to the atmosphere by a series of spaced orifices 258in the inner wall of the member adjacent its rear end. The control valveis in the nature of a needle valve 251 comprising a stem 259 having aneedle point 260 for cooperating with a beveled seat 26L The seat 26!surrounds an opening which connects the rear end of the cylinder 254with the cavity 268. The valve stem 259 extends through one of thepiston rods 25! and a flexible control wire 262 is connected with itsforward end. The wire 262 may extend to a remote conveniently accessibleoperating or adjusting lever, or the like, not shown, and may beprotected by a flexible protective housing 253. It will be seen that theposition of the valve head or needle 260 may be readily altered bysimple operation of the control wire.

The invention provides means for cooling the inner throat member 246 ofthe nozzle. The hollow connecting rods 248 communicate with the forwardend of the annular cylinder 254 and ducts 265 lead from the forward endsof the hollow rods to the interior of the throat member 246. A row ofcircumferent'ally spaced orifices 261 is provided in the inner wall ofthe member 246. A

row of similar orifices 2Bl is formed in the trail- I 246 serves to coolthe same, and the air discharged 1 from the orifices forms a protectiveboundary for the surfaces of the member and provides a boundary layercontrol action to increase the efliciency of the nozzle. It will beobserved that the airflow through the annular cylinder 254 and theannular cavity 268 likewise cools the outer throat member Referring nowprimarily to Figure 1, the variable area propulsive nozzle operation isas follows: The upper half'of the figure shows the throat members 246and 241 ina fully retracted position to form a nozzle opening of maximumeffective opening area and the lower half of the figure shows the throatmembers 246 and 241 in a fully-extended position to form a nozzleopening of minimum effective opening area.

In general, the positions of the throat members are varied between theextreme retracted and extended positions illustrated, for the purpose ofcorrespondingly varying the turbine exhaust back pressure and theattendant turbine speed. The position of the throat members isdetermined by the pos tion of the stem 259 of the needle valve 251 withres ect to the piston rod and may be controlled throu h the Bowden typeof flexible wire control cable 262 which leads through the flexible houing 263 to a suitable manual or remote ad ustin' device not shown. Airunder substantially constant pressure is supplied from a su tab e sourceto the inner or rod end of the to flow through passageways in one ormore of the tie rods 248 into the interior cavity 266 of the innerthroat member 246 for cooling purposes. The cooling air thus introducedinto the throat member is allowed to escape through a plurality ofinwardly directed apertures 261 located at the throat member and alsothrough a plurality of apertures 28l in the trailing edge of the throatmember. In addition to the cooling of the nozzle parts, the air escapingfrom the apertures 261 and 281, and also at 258, tends to effectboundary layer control within the nozzle elements favorable to increasednozzle efflciency.

Having described only a typical form of the invention, I do not wish tobe limited to the specific details herein set forth, but wish to reserveto myself any variations or modifications that may coaxially positionedoutside of and adjacent the annu ar cylinder 254 conta ned with n theouter throat member 241, by way of a tube 256 which makes connectiontoan ex osed end of one of the several ho low piston rods 251 as bestshown in Fi ure 3 upon which the outer throat member 241 is s idably suported. Air reaches the cylinder, from nine 256 through the central bore255 in the piston'rod and throu h the lateral ports 211. The duct 218 beeds sufiicient a r from the rod end of t e cylinder to the headend ofthe cylinder to a tia l eoualize the pressure on either side of theiston 253. The frictional forces of the gases flowin out of the nozzletend to carry the throat members out to the extended position. Suchmotion causes the needle val e to o en,

which a lows the air pressure to dro in the head end of the annular cylnder 254 and the resulting 'ove ba anc'ng pressure in the rodend-of theThe throat members outer end of said nozzle means coupling said firstand second annular throat members together for simultaneous longitudinalmotion with respect to the axis of said nozzle and said contraction insaid nozzle whereby the effective length and cross sectional area of thethroat ofsaid nozzle may be varied. and means to impart longitudinalmovement to said throat members.

2. Nozzle means for the exhaust of a propulsive unit, comprising anozzle for communicating with the exhaust of said unit,- a contractionin said nozzle forming a passage of reduced cross seccoaxiallypositioned within said nozzle intermeditional area, a first annularshaped throat member ate the'exhaust of said unit and the saidcontraction, a second annular shaped throat member coaxially positionedoutside of and adjacent the outer end of said nozzle, means couplingsaid first and second annular throat members together for simultaneouslongitudinal motion with respect'to the axis of said nozzle whereby theeffective length and cross sectional area of said nozzle maybe varied, acylinder contained in said second annular shaped throat member, a pistonin said cylinder,

a coupling between said piston and said nozzle,

means to introduce fluid under pressure into said cyl nder and means tovary the pressure of said extended position, air from the spacesurrounding the nozzle is drawn through the opening formed between theend of the nozzle body 250 and the outer throat member 241 to co-minglewith the jet of combustion gases as illustrated by the arrows 219 and280 and an augmenter action is obta ned.

A port on of the compressed air in roduced into the rod end of theannular cylinder 254 is allowed fluid in said cylinder to move andposition said annular throat members with respect to said nozzle.

3. Apparatus according t-o claim 1 in which the said annulus of thethr'oatmembers have inwardly cambered streamline cross sections formingin effect a variable venturi shaped nozzle opening.

4. Apparatus according to claim 2 in which the said annulus of thethroat members have inwardly cambered streaml ne cross sections forming..in eflect. a variable venturi shaped nozzle opening.

5. Nozzle means for the exhaust of a propulsive unit. comprising anozzle for communicating with the exhaust of said unit, a contraction insaid nozzle forming a passage of reduced cross sectional area. a firstann lar shaped t roat member coaxi lly. positioned within said nozzleintermediate said exhaust and said contraction, a second 7 annularshaped throat member coaxially positioned outside of and adjacent theouter end of said nozzle, means coupling said first and second annularthroat members together for simultaneous longitudinal motion withrespect to the axis of said nozzle whereby the effective length andcross sectional area of said nozzle may be varied, a cylinder containedin said second annular shaped throat member, a piston in said cylinder,a coupling between said piston and said nozzle, means to introduce fluidunder pressure into said cylinder and follow-up valve means to vary thepressure of said fluid in said cylinder in accordance with a function ofthe longitudinal position of said annular throat members with respect tosaid nozzle.

6. Apparatus according to claim 1 with cooling ducts in at least one ofsaid throat members and means to pass cooling fluid through said duct.

7. Nozzle means for a reactive propulsion unit having an exhaustcomprising a nozzle communicating with the exhaust of the unit, a hollowtubular throat member movable axially with respect to the nozzle to varythe efiective area thereof, the hollow throat member having portsleading from its interior to its external surface where they communicatewith the interior of the nozzle, fluid pressure actuated means formoving the throat member, a remote control for the fluid pressureactuated means, and means for circulating coolant through the hollowmember for discharge from said ports.

8. Nozzle means for the exhaust of a reactive propulsion unit comprisinga nozzle communicating with said exhaust, a throat member movableaxially relative to the nozzle to vary the effective area thereof, and acontrol for the throat member including a cylinder and piston for movingthe member, means for supplying actuating fluid under a substantiallyconstant pressure to the cylinder, valve means for unbalancing thepressures at the, opposite sides of the piston whereby said unbalancedpressures tend to move the member in one direction, the friction of thenozzle gases tending to move the member in the other direction, andmeans for changing the setting of the valve means whereby saidunbalanced pressures and said friction will be in equilibrium with themember in selected axial positions.

9. Nozzle means for the exhaust of reactive propulsion unit comprising anozzle for communicating with said exhaust. throat means for varying theeffective area of the nozzle comprising a member movable axially withrespect to the nozzle and through which the nozzle gases pass, acylinder and piston for moving the member axially, means for conductingfluid under substantiallv constant pressure to the cylinder, a valve forunbalancing the pressures at opposite sides of the piston and adiustableto vary such 50 unbalancing of pressures, the unbalanced pressurestending to move the member in one direction and the frict on of thenozzle gases tending to move the member in the other direction. andremotely controlled means for changing the position of the valve so thatsaid unbalanced o essures and said friction come into equilibrium withthe member in any selected axial position.

10. Nozzle means for the exhaust of a gas reactive propulsion unitcomprising a nozzle communicating with the exhaust of the unit, throatmeans for varying the effective area of the nozzle comprising a membermovable axially with respect to the nozzle and through which the nozzlegases pass, a cylinder carried by the member, a

the member in the other direction, and means for moving the valve sothat said friction and said unbalanced pressures will come intoequilibrium when the member is positioned as determined by the settingof the valve.

11. Nozzle means for the exhaust of a reactive gas propulsion unitcomprising a nozzle for communicating with the exhaust of the unit, athroat restriction on the wall of the nozzle, a tubular open endedthroat member at a side of the restriction, means supporting the memberfor movement axially relative to the restriction to vary the effectivearea of the nozzle, the member having a divergent internal throatsurface substantially axially al gned with the internal surface of saidrestriction, and means for moving the member.

12. Nozzle means for the exhaust of a reactive gas propulsion unitcomprising a nozzle for communicating with the exhaust of the unit, athroat restriction in the nozzle having a passage of minimum crosssectional area at the discharge end of the nozzle, a tubular throatmember having an internal surface substantially axially aligned with theinternal wall of said throat restriction, means sup orting the memberfor movement from a pos tion with its forward end at said discharge endof the nozzle so as to constitute a rearward continuation of saidrestriction to a positionwhere said member is soaced rearwardly of saidend of the nozzle, and means for moving said member.

13. Nozzle means for the exhaust of a reactive gas propulsion unitcomprising a nozzle for communicating with the exhaust of the unit,a-throat restriction in the nozzle, said restriction reducing theeffective cross sectional area of the nozzle to the greatest extent atthe discharge end of the nozzle, a tubular throat member having aninternal surface substant ally axial y ali ned with the internal wall ofsaid throat restriction. means sup orting the member for movement from aposition with its forward end at said discharge end of the nozzle so asto constitute a rearward continuation of said restrict on to a positionwhere it is spaced rearwardl'v of sai end of the nozzle. means for circlating coolant throu h the member. and means for moving said member.

14. Nozzle means for the exhaust of a. reactive gas ropulsion unit coprising a nozz e for commun cat n wi h the exhaust of the u it. a throatrestriction in the noz le. said restriction'b in adjacent the dischargeend of the nozzle. a tubular throat member, means su por ing th memberfor mo ement from a position where it forms a rearward conti uation ofsaid restrict on to a position where it is spaced rearwardly of said endof the nozzle, the member having an internal cavity and orifices leadingfrom the cavity through the internal wall of the member, means forcirculating cooling air through the cavity for discharge from theorifices, and means for moving said. member.

15. Nozzle means for the exhaust of a reactive municating with theexhaust of the unit, a throat restriction in the nozzle, a throat memberat each restriction in the nozzle, a throat member at eachside of therestriction, means supporting the members for movement in unison axiallyrelative to the restriction to vary the effective area of the nozzle,cylinder and piston means for moving the members, means for supplyingactuating air under pressure to the cylinder and piston means, themembers having internal cavities, and means for bleeding a portion ofsaid air under pressure into the cavities to cool the members.

17. Nozzle means for the exhaust of a reactive gas propulsion unitcomprising a nozzle for communicating with the exhaust of the unit, athroat restriction in the nozzle, a hollow tubular throat membersupported for movement toward and away from said restriction, the memberhaving orifices in its inner wall, cylinder and piston 10 striction, atubular throat member in downstream relation to the restriction andhaving an eilective internal diameter slightly larger than that of therestriction, means supporting the throat members for axial movementrelative to the restriction, and means for imparting such movement tothe members.

20. Nozzle means for discharging gases in the form of a propulsive jetcomprising a tubular nozzle for the discharge of said gases, arestriction at the discharge end of the nozzle, an axially movabletubular open ended member of airfoil cross section extending rearwardlybeyond the means for moving the member, means for supplying actuatingair under pressure to the cylinder and piston means, and means forbleeding a portion of the air under pressure into the interior of thehollow member for discharge from said orifices.

18. Nozzle means for the exhaust of a reactive gas propulsion unitcomprising a nozzle for communicating with the exhaust of the turbine, athroat restriction in the nozzle, a hollow tubular throat membersupported for movement toward and away from said restriction, the memberhaving orifices in its inner wall, cylinder and piston means for movingthe member, means for supplying actuating air under pressure to thecylinder and piston means, and means for bleeding a portion of the airunder pressure into the interior of the hollow member for discharge fromsaid orifices, said orifices being directed rearwardly so that the airdischarged therefrom forms a boundary layer on the inner surface of thetubular member.

19. Nozzle structure for the exhaust or a reactive gas propulsion unitcomprising a tubular nozzle for communicating with the exhaust, a throatrestriction in the nozzle adjacent the discharge end of the same, atubular throat member in the nozzle in upstream relation to therestriction having an eflfective internal diameter smaller than theeflective diameter or the rerestriction to form an extension of thenozzle; and fluid pressure actuated means for moving the member andoperable to move the member rearwardly from the restriction to leave apassage through which air is induced to flow so as to enter said memberby the ejector efiect of the gases discharging through said member, theminimum internal diameter of said member being substantially the same asthe minimum internal diameter of said restriction.

21. Nozzle structure for the exhaust of a reactive gas propulsion unitcomprising a tubular nozzle for communicating with the exhaust, a throatrestriction in the nozzle adjacent the discharge end of the same, atubular throat member through which the gases pass, means for.supporting the member for axial movement relative to the restrictionincluding movable support means spaced radially from the member, armsextending radially from the member to support means, the arms includingtubular metal cores, and refractory material shields on the cores, andmeans for circulating coolant through the cores.

NATHAN C. PRICE.

REFERENCES CITED The following references are of record in the idle ofthis patent:

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